initial work to split into dart_filament and flutter_filament

flutter_filament/ios/Classes/FlutterFilamentPlugin.m

@@ -0,0 +1,18 @@
+#import "FlutterFilamentPlugin.h"
+#if __has_include(<flutter_filament/flutter_filament-Swift.h>)
+#import <flutter_filament/flutter_filament-Swift.h>
+#else
+// Support project import fallback if the generated compatibility header
+// is not copied when this plugin is created as a library.
+// https://forums.swift.org/t/swift-static-libraries-dont-copy-generated-objective-c-header/19816
+#import "flutter_filament-Swift.h"
+#endif
+
+#include "FlutterFilamentApi.h"
+
+@implementation FlutterFilamentPlugin
++ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
+  [SwiftFlutterFilamentPlugin registerWithRegistrar:registrar];
+  ios_dummy();
+}
+@end